Abstract
BACKGROUND: In the intracellular environment, motor-driven cargo must navigate a dense cytoskeletal network among abundant organelles. RESULTS: We investigated the effects of the crowded intracellular environment on early endosomal trafficking. Live-cell imaging of an endosomal cargo (endocytosed epidermal growth factor-conjugated quantum dots) combined with high-resolution tracking was used to analyze the heterogeneous motion of individual endosomes. The motile population of endosomes moved toward the perinuclear region in directed bursts of microtubule-based, dynein-dependent transport interrupted by longer periods of diffusive motion. Actin network density did not affect motile endosomes during directed runs or diffusive interruptions. Simultaneous two-color imaging was used to correlate changes in endosomal movement with potential obstacles to directed runs. Termination of directed runs spatially correlated with microtubule-dense regions, encounters with other endosomes, and interactions with the endoplasmic reticulum. During a subset of run terminations, we also observed merging and splitting of endosomes, deformation of the endoplasmic reticulum, and directional reversals at speeds up to 10-fold greater than characteristic in vitro motor velocities. These observations suggest that endosomal membrane tension is high during directed run termination. CONCLUSIONS: Our results indicate that the crowded cellular environment significantly impacts the motor-driven motility of organelles. Rather than simply acting as impediments to movement, interactions of trafficking cargos with intracellular obstacles may facilitate communication between membrane-bound compartments or contribute to the generation of membrane tension necessary for fusion and fission of endosomal membranes or remodeling of the endoplasmic reticulum.
🔬 Techniques
✨ Fluorophores
🧪 Sample Preparation
🔬 Cell Lines
💾 Data Repositories
🏛️ Research Organizations (ROR)
Affiliated research institutions:
📊 Figures
Figure 1
Motility in the early endosomal population A. Early endosomes move in rapid bursts towards the perinuclear region interrupted by periods of little net movement. Kymographs of early endosomes were cont...
Figure 2
The effect of cytoskeletal disruption on early endosomal motion A. Potential roles for actin filaments in early endosomal movement. Early endosomes (green), actin filaments (blue), myosin motors (red)...
Figure 3
Parsing of trajectories into directed runs and pauses A. Early endosomal trajectories exhibited directed motion punctuated by pauses. A representative EGF-Qdot trajectory (black) with directed motion ...
Figure 4
The motion of individual EGF-Qdot-containing early endosomes during encounters with other Rab5-positive early endosomes A. EGF-Qdots merge with and split away from other early endosomes during their t...
Figure 5
Early endosomal movement is affected by interactions with the ER and multiple MTs. A. Early endosomes remain attached to the ER for long periods during which repeated deformation of the ER occurs. The...
Figure images are served from the NIH/NLM PubMed Central Open Access Subset or Europe PMC; copyright remains with the publishers and authors.
💬 Discussion
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